Air sterilizing method and apparatus



May 6,1952 w. M. GRosvENoR, JR 2,595,574

AIR uQQERILIZING METHOD AND -MDPARATUS FiledApril 12, 195o FIG. l

F-laz l Plas TTORNEY` Patented May 6, 19752 2,595,674 AIR srEnILizING METHOD AND APPARATUS William M. Grosvenor, Jr., New York, N. Y., assignor, by mesne, assignments, to StaywellCorporation, New York, N. Y., a corporation of New York Application April12, T950, Serial No. 155,518

Claims.

This invention relates to an improved process and apparatus for supplying triethylene glycol vapor in effectivey amount for disinfecting the air ofv a closed space such Ias a room without supersaturating the air and without the accompanying objectionable fog, condensation on furniture, etc., which such supers'aturation produces.

It is known that, triethylene glycol vapors are effective for the disinfection of air and that a relatively narrow margin exists between the concentration of triethylene glycol vapor required for optimum bactericidal action and the saturation point of, this. vapor in air of various relative humidities and temperatures.

The present. invention provides an improved process and vapor dispensing device whereby the air in a closed space such as a schoolroom can be continuously supplied with triethylene glycol vapor to maintain an effective concentration of such vapor in the closed space without. danger of. supersaturation of the air;`

It will be appreciated that the relativeVv humidityand temperature of the air in aroom. are subject to considerable variation and that the rate at which the room air is changed by natural or artificial ventilation will also vary;

Vapor dispensing devices have been proposed whichy are manually'regulated and which can be adjustedto. provide for larger or smaller amounts of vapors. But with manual regulation there. may at times be insufiicent vapor for the purpose intended. andvat othertimes an excess. of vapor may be. supplied with consequent condensation on and dangers to the contents of the room.

The' improved process and apparatus yoi' thel present invention do not require manual operation or regulation, but nevertheless enable effectivev amounts of triethylene glycol vapors to be supplied tothe room withoutdanger of super-- saturation and condensation'.

According to the present invention, the glycol vapors areprimarily supplied by an electrically heated vaporizer which vaporizes the glycol into a currentof air'passingtherethrough and which recirculatesf the air in the: room-- through the va# porizer.: InV addition, a.. small supplemental va'-` porizerv vaporizes only a small amount of glycol into the air passingY therethrough. Anda resistancevcell is located in the path of the air from the supplemental vaporizer with electrical connections which turn ofi the main vaporizer when the air'in the'room approaches saturation with glycol vapors, and turns the main vaporizer` on egainfswhen the air falls below a predetermined degreeofsaturation;

From an apparatus standpoint, theinvention includes a main electrically heated glycol vaporizer, a small supplemental electrically heated glycol vaporizer, a resistance cell located in the path of the air from the.- supplemental vaporizer. and electrical connections and relay connected to the resistance cell for turning on and oi the main vaporizer, or both the mainl and supplemental vaporizers, when the, glycol vapor content in the room approaches saturation.

The resistance cell is typified by a sheet of glass having a conductive layer upon it and a narrow area between the conductive layer which is non-conductive such as-is made by taking a sheet of mirror glass and scratching away the conductive layer to leave a narrow strip of glass uncovered by the conductive material and connecting the electrical contacts to the conductive material on each side ofthis insulating strip. The contacts of the cell are connectedthrough relays with a switch which. turns off or on the vaporizer depending on whetherl the celly acts as a conductor or an insulator.

This resistance cell is located adjacent the, supplemental vaporizer where thefair with only a small increase in glycol vapor content impinges on the cell and when the glycol vapor content impinging on the cell approaches saturation.I it

condenses on the insulatingsurface of thev cell` and converts the insulating surfaceintoa conducting surface. A salt. soluble in the glycol,

such as copper chloride-, is deposited on thssn-Y sulating area to aid in holding the glycol thatA impinges on itand when the glycol is-adsorbed` to an extent sufficient to form a conducting layer, it closes the circuit and activates the relays which operate the switch and turnsof the main va,- porizer.

The cell isalso providedw-ith a heater which is turned on when the vaporizer is turned ofi, and thisheater is so arranged andis-of such a na.- ture thatit slowly evaporates-or tends toY evaporate the adsorbed. layer or" glycol onl the/cell. So long as the glycol-laden air impingingonfthe.

cell is sufliciently'highrin.-glycol vapor, the cell remainsconductive and the vaporizer is shut oii'; When the glycol vapor in the air impingington the cell falls below a certaiirdegreaof saturation, the heat vaporizes theV glycol yfaster than/it. is adsorbed until the; cell becomes a non-conductor:

and this causes the relays to act; to throw: the

switch in the opposite direction to turnlon th'e main vaporizer, and: to turn oi the heater.v forv the cell.

When this `supplemental vaporizerfis: operated continuously and the glycol: vapor inthe room` approaches saturation. a conductive layer will be formed on the cell and the main vaporizer will be out ofi by the relay and actuating mechanism and the heater will be turned on. The heating of the cell will then act in opposition to the adsorption of glycol vapor from the stream of air impinging on the cell. So long as the glycol vapor in the air is sufficiently high, approaching saturation, the air impinging on the cell will have an increased amount of glycol vapor in it which will be suicient to maintain the conductive layer of glycol on the cell even when the heater is operating. But as the glycol vapor in the room falls below a predetermined point the heater will remove glycol from the cell faster than it will be adsorbed until the cell becomes non-conductive whereupon the electrical circuit is disconnected and the main vaporizer turned on and the heater for the cell turned oil.

Instead of operating the small supplemental Vaporizer continuously, it can also be connected with the same switch mechanism and relay which turns off and on the main vaporizer so that the supplemental vaporizer will be turned off and on at the same time. In this case, the heater for the cell will be turned on when both vaporizers are turned off; and when the cell becomes a nonconductor, the relay and switches will be operated to turn on both vaporizers.

'Ihe main and supplemental vaporizers can advantageously be combined in a single cabinet with the resistance cell located between them and with the air from the room forced by a fan first through the supplemental vaporizer where its glycol vapor content is increased only slightly, alter which the air passes over the cell and then through the main vaporizer where a much larger increase in glycol vapor content takes place before the air is discharged back into the room. In this case, when the air approaches saturation, the air from the supplemental vaporizer impinging on the cell may become saturated or more nearly saturated so that a conductive glycol layer will more readily form. And when the glycol vapor content is high enough in the room, the main vaporizer will be shut off or both vaporizers may be shut oi. Where the supplemental vaporizer continues in operation, the main vaporizer will be shut oil until the glycol vapor content of the air from the supplemental vaporizer impinging on the cell is insunicient to overcome the vaporizing effect of the heater. When that occurs and the cell becomes a non-conductor, the break in the electrical circuits operates the switch to turn on the main vaporizer which stays on until'the vapor content increases to the point of reestablishing the conductive layer in the cell.

'The invention is applicable to existing installations having an electrically heated vaporizer. In such case, there is added a small supplemental vaporizer, a resistance cell adjacent the supplemental vaporizer, electrical connections and relay and switch to control the electric heater of the main vaporizer, or the heaters o both vaporizers. In .this arrangement, the resistance cell will be located in the path of the air discharged from the vaporizer and the supplemental vaporizer.

The invention will be further described in connection with the accompanying drawings which illustrate in a somewhat conventional and diagrammatic manner an arrangement of apparatus embodying the invention and adapted for the practice of the process of the invention, but it will be understood that the invention is illustrated thereby but is not limited thereto.

In the accompanying drawings,

Fig. l shows in a conventional and diagrammatic manner a portion of a room with a vaporizer and cell located there, and with the electrical connections omitted;

Fig. 2 is a diagrammatic iront view of the cell;

Fig. 3 is a side view of the cell showing the cell heater; and

Fig. 4 shows one form of wiring connections and arrangements and relay for operating the apparatus.

In Fig. 1 a portion of a room is shown conventionally with the main vaporizer l, the supplemental vaporizer la and the resistance cell 4 mounted in a single cabinet through which air is forced by the fan 2 and its operating motor 3. The air is drawn in from the room, and forced rst through the small supplemental vaporizer la where only a very small increase in glycol vapor content takes place, then over the cell 4 and then through the main vaporizer l and back into the room. The air is, in this way, repeatedly recirculated from the room through the vaporizers and back to the room until the content of glycol vapors in the air of the room approaches saturation. The air passing from the small supplemental vaporizer over the resistance cell will have a slightly increased content of glycol vapor from that of the air in the room which is recirculated by the fan through the supplemental vaporizer.

One form of resistance cell is shown conventionally in Figs. 2 and 3. The front of the cell as shown in Fig. 2 has two side portions 5 and 5, such as the conductive metal layer on the back of a mirror, with a clear path 1 between them forming an insulating or non-conducting area until a film of glycol vapor is formed thereon. This area 1 is coated with a layer of a glycol soluble salt such as cupric chloride to aid in the forming of a conductive glycol layer when the glycol vapor content in the air approaches saturation. On the back of this cell is a heater 8 for heating the cell and aiding in the removal of the layer of glycol therefrom.

A conventional arrangement of relay and connections for operating the apparatus is shown in Fig. 4, this relay consisting of a one-stage amplifier using a tube 9 (ll'lN'l) and a single-pole, double-throw relay together with circuit components shown in the diagram. Current is supplied through the lines Il) and Il, one of which is connected through the line i2 and the branch line I3 to the Vaporizer l and then through the line lll to the terminal l5 which is normally connected as shown with the switch member i6, which in turn is connected through the lines 20 and 2l to the line Il. Another branch connection i1 leads from the line 2 to the cell heater 8 and then through the line I8 to the terminal i9 of the relay.

It will be seen that the plate 22 and screen 23 of the tube are connected through lines 24, 25 and 2l to the line ll; while control grid 26 is connected through the grid resistor 2T to the other side of the line l. The cathode 23 is connected to a potentiometer set 2G through the line 3D. The electromagnet 3l for operating the switch I3 is connected with the circuit of the plate 22, the SO'mfd. condenser 32 across the relay coil serving to convert the pulses of alternating current into a direct current preventing chattering of the relay. f

Assuming at any instant the polarity of the A. C. supply is as indicated, it will be seen that plate22 and' screen 23 of the tube are connected to the positive `side of the line, While control grid 26 is connected through grid resistor 2l to the negative side of the line. Cathode 2B is connected to the potentiometer set to make the cathode potential sufliciently positive (negative grid bias) with respect to the grid 26 so that the plate current flowing is insuiiicient to operate the relay.

The above conditions hold when the measuring cell has a very high resistance and so has a negligible effect upon the potential of grid 2S. Thus, when the resistance of the cell is of the order of magnitude of the 3.9 niegohm resistor 21, insufficient plate current flows to operate the relay.

When, however, a film of glycol is deposited on the cell, positive, potential derived from the 0.1 meg. potentiometer 3S, connected through the line 34 to the cell 4, which in turn is connected` through the line 35 with the grid 2S, causes a current flow through the cell and the 3.9 meg. grid resistor 21, reducing the negative bias of the grid 26 with respect to the cathode 2B. The plate current consequently increases, operating the relay and causing the switch member I6 to contact with the terminal i9, which shuts 01T the current to the vaporizer I and turns on the cell heater 8 until in due time the original conditions are restored.

In the foregoing it has been assumed that one supply terminal was positive and the other negative. The fact that the supply is actually A. C. means that the plate current flows in pulses sixty times a second, while the condenser 32 across the relay coil 3| serves to convert these pulses into a direct current, preventing chattering of the relay. During periods of reverse polarity, no current flows in the plate 22 as the tube conducts in only one direction.

The supplemental vaporizer ia is connected with the line I through the branch connection 40 and with the switch 4I which is a manually operated switch and which may be connected either with the contact S2 and the line 43 with the line II; or with the contact 44 and the line 5 which leads, to the line i4. When the switch 4I is connected with the contact 42, the supplemental vaporizer will be continuously operated. When the switch 4I is connected with the terminal 4&3, the supplemental vaporizer will be shut off when the main vaporizer I is shut off and will be turned on when the main vaporizer I is turned on.

In the operation or the apparatus described, the switch I6 will normally be in contact with the terminal I5 and current will pass through the main vaporizer I and the air laden with glycol vapors there formed will be continuously discharged into the room until the vapor content approaches saturation. The supplemental vaporizer will vaporize a small amount of glycol vapors and increase the content of such vapors passing over the resistance cell so that this air will approach more nearly to saturation than the air in the room. This cell 4, located in the path of the glycol-laden air coming from the supplemental vaporizer will remain non-conductive until the glycol vapor approaches saturation in the air, when it will be condensed, or adsorbed on the surface of the cell and will form a conductive layer thereon. Thereupon, the relay will he operated to disconnect the switch I6 from the contact I5 thus shutting off the current to the main vaporizer, or to both the main and supplemental vaporizers, and connecting the switch i6 with the contact I9, turning on the current; to the cell heater.

The moderate application oi heat to the cell will, after a sullcient period of time, vaporize the layer of glycol and render the cell again nonconductive through the insulating area l. When the supplemental vaporizer continues in operation during the time the main vaporizer is shut off and the cell heater is turned on, the heating of the cell will act in opposition to the adsorption of glycol vapor from the stream of air impinging on the cell. So long as the glycol vapor in the air is suiiiciently high, approaching saturation, the air impinging on the cell will have an increased amount of glycol vapor in which it may be suflicient to maintain the conductive layerof glycol on the cell, even when the cell heater is operating. But, as the glycol vapor in the room falls below a predetermined point, the heater will remove glycol from the cell faster than it will be adsorbed until the cell becomes non-conductive, whereupon the heater of the cell is disconnected and the main vaporizer turned on. The glycol vapor in the room will thereupon be increased and the air passing over the small supplemental vaporizer will have its glycol vapor content further increased until the air again approaches a suiiicient concentration of glycolvapors to form a conductive layer of glycol on the cell, whereupon the main vaporizer will be again turned oil and the cell heater again turned on.

The improved method and apparatus of the present invention are automatic in operation and enable the glycol vapor content of the room to be increased to an effective degree short of saturation, while avoiding saturation and supersaturation of the air in glycol vapor.

I claim:

1. An apparatus for supplying triethylene glycol vapor in eective amount for disinfecting the air of a closed space without supersaturating the air therein including a main electrically heated vaporizer for vaporizing the glycol vapors into a current of air, means for recirculatingr the air in the closed space through said main vaporizer, a small supplemental vaporizer for vaporizing only a small amount of glycol vapor into a current of air with means for circulating the air of the closed space therethrough, a resistance cell located in the path of the air from the supplemental vaporizer and having a normally nonconductive area which is adapted to become conductive by the adsorption of glycol thereon, a

heater for heating said cell to effect gradual removal of glycol vapors therefrom when a layer of glycol is formed thereon, electrical connections for heating the main vaporizer and the heater of said cell, a relay connected with said cell and operated thereby when a conductive layer of glycol is formed thereon, to disconnect the heater of the main vaporizer and to connect the heater of the cell, and to connect the heater of the main vaporizer and disconnect the heater of the cell when the conductive layer of glycol is removed from the cell, and means for selectively operating said supplemental vaporizer in simultaneity with the main vaporizer and independently of the main vaporizer.

2. An apparatus as dened in claim 1 provided with electrical connections for disconnecting the supplemental vaporizer when the main vaporizer is disconnected and for turning on the supplemental vaporizer when the main vaporizer is turned on.

3. An apparatus as dened in claim 1 in which the supplemental vaporizer is continuously heated both when the main vaporizer is turned on and turned off.

4. An apparatus as defined in claim l in which the supplemental vaporzer, the resistance cell and the main vaporizer are enclosed in a single chamber with means for circulating the air from the room rst through the supplemental vaporizer, then over the resistance cell and then through the main vaporizer and back into the room.

5. In a system for supplying triethylene glycol vapor to the air of a closed Space by a main electrically heated vaporizer, the combination of a small supplemental vaporizer for vaporizing only a small amount of glycol vapor into the air of the room circulating therethrough a resistance cell located in the path of the air from said supplemental vaporizer and having a normally nonconductive area which is adapted to become conductive by the adsorption of glycol thereon, a heater for heating said cell for effecting grad-ual removal of glycol vapors therefrom when a layer of glycol is formed thereon, electrical connections for heating the main vaporizer and for heating said cell, a relayT connected with said cell and operated thereby when a conductive layer of glycol is formed thereon to disconnect the heater of the main vaporizer and to connect the heater of the cell, and to connect the heater of the main vaporizer and disconnect the heater of the cell when the conductive layer of glycol is removed from the cell, and means for selectively operating said supplemental vaporizer in simultaneity with the main vaporizer and independently of the main vaporizer.

WILLIAM M. GROSVENOR, JR.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS OTHER REFERENCES Weaver: Measurement of Water in Gases by Electrical Conduction in a Film of Hygroscopic Material Journal of Research of National Bureau of Standards, RP 1865, volume 40, March 1948, pages 169 to 214. 201-631-1. 

